1. Field of the Invention
The present invention relates to a chemical treatment apparatus that is suitable for performing the deposition of a metal or treatment such as etching by supplying a chemical to a surface of a substrate such as a silicon wafer.
2. Related Background Art
Semiconductor devices in which high-density interconnections are formed by forming through holes, non-through holes, grooves, etc. on a substrate such as a silicon wafer have hitherto been manufactured. To that end, a process in which a surface of the substrate is subjected to a plating treatment and an etching treatment by use of a chemical is frequently adopted. For example, through holes, non-through holes and grooves having a prescribed shape are formed in a substrate by performing an etching treatment or a substrate in which holes and grooves are formed beforehand is filled with a metal by the electroplating treatment, whereby electrical interconnections are fabricated.
Three types of apparatuses have been used as chemical treatment apparatuses in the plating treatment and the etching treatment. These apparatuses are of (i) the vertical type in which with a substrate is vertically set, a chemical and a surface to be treated (hereinafter, referred to as “treating surface”) of the substrate are brought into contact with each other; (ii) the face down type in which a treating surface of a substrate is brought into contact with a jet flow of a chemical with this surface facing downward; and (iii) the face up type in which a treating surface of a substrate is brought into contact with a jet flow of a chemical with this surface facing upward.
FIG. 6 is a schematic diagram of a conventional face up type electroplating apparatus. In FIG. 6, a silicon wafer 601 having a Cu seed film is disposed on a wafer-holding jig 602 with its treating surface facing upward. The silicon wafer 601 and wafer-holding jig 602 are installed in an outer cell 621 having the shape of an inverted cup, which is filled with a plating liquid 600.
An inner cell 611 is installed above the silicon wafer 601 within the outer cell 621, and an anode 613 having the shape of a grating board is attached to the bottom end portion of this inner cell 611. From gaps 612 of this anode 613 having the shape of a grating board, the fresh plating liquid 600 fed from an external liquid-feeding pump, which is not shown in the figure, is discharged toward the treating surface of the silicon wafer 601. The plating liquid 600 is recovered from a chemical discharge port 622 provided in the upper part of the outer cell 621 into an external receiving tank, which is not shown in the figure. By applying a voltage to between the anode 613 having the shape of a grating board and the silicon wafer 601 having a seed film, it is possible to cause a metal to deposit on the seed film of the silicon wafer 601. At the outer circumferential portion of the silicon wafer 601, a chemical seal 603 is formed to prevent the plating liquid 600 from entering the wafer-holding jig 602.
Furthermore, in addition to the method that uses the above-described anode 613 having the shape of a grating board, Japanese Patent Application Laid-Open No. 2001-015454 describes the use of a partition board that has a large number of discharge pores having a pore diameter of 0.1 mm to 1 mm. Also, Japanese Patent Application Laid-Open No. 2001-024308 (Patent Document 2) describes the use of a board in which a large number of through holes having an inside diameter of 3 mm are formed in a 30 mm thick plate body. By adopting such configurations, it is possible to prevent the drop of a chemical from the inside of a fine tube due to surface tension when the supply of a plating liquid is stopped.
Other than the face up type, a vertical type chemical treatment apparatus is frequently used in the electroless plating treatment, etching treatment, etc. FIG. 7 is a schematic diagram of a vertical type chemical treatment apparatus. In FIG. 7, a wafer 701 attached to a wafer-holding jig 702 is vertically immersed in a treatment vessel, with its treating surface facing toward a chemical delivery nozzle 714. In FIG. 7, the silicon wafer 701 attached to the wafer-holding jig 702 is vertically immersed in the treatment vessel 721 in such a manner that the treating surface faces toward the chemical delivery nozzle 714. An electroless plating liquid or an etching liquid 700 discharged from a nozzle 714 is fed from an overflow vessel 706 to a liquid feeding pump 723, is circulated and is used again in the chemical treatment.
Recent years have seen increasingly high requirements for high-density design of semiconductor devices that use a silicon wafer as a substrate. When a substrate in which through holes, non-through holes, grooves, etc., are formed is subjected to an etching treatment and a plating treatment using a chemical, it is necessary to rapidly replenish the chemical, because it is used up by reactions that occur in the holes and grooves. By rapidly replacing the chemical with a fresh one, it is possible to constantly keep the concentrations of effective components of the chemical at constant levels, and hence, it is possible to realize uniform, high-grade, high-speed treatment.
However, the recovery of the concentrations of the effective components that have been consumed at reaction interfaces is rate controlled by the diffusion rates of the effective components in the solution. For this reason, it is necessary to increase the diffusion rates of the effective components to the highest possible levels. However, in the vertical type shown in FIG. 7, a chemical does not diffuse uniformly due to the effect of gravity and in particular, the replacement of the chemical at the bottoms of the grooves tends to become insufficient. Furthermore, the distribution of the liquid flow on the surface of a substrate also tends to become nonuniform. For this reason, a variation in the film thickness distribution of a coating film and a variation in the etched amount occur.
In contrast, in the case of the face up method shown in FIG. 6, the structure of the apparatus enables a chemical to diffuse easily in comparison with the vertical type, variations due to gravity do not occur, and the possibility that a gas generated on the treating surface stagnates is weak. Furthermore, by installing a device for stirring a plating liquid in the interior of the outer cell, it becomes possible to diffuse the chemical more rapidly, thereby making the distribution of the chemical uniform. However, in the case of through holes, non-through holes and grooves, which have an inside diameter and a minimum diameter that are as small as not more than 200 μm and a high aspect ratio of not less than 1:3, it takes a very long time before the consumed chemical in the through holes, non-through holes and grooves diffuses to the outside. Furthermore, it is conceivable that in some cases the exhausted chemical does not completely diffuse and stagnates in the interior of the through holes, non-through holes and grooves, causing nonuniform treatment and prolongs the treatment time. Also, there is a possibility that the chemical itself does not sufficiently flow into the through holes, non-through holes and grooves, resulting in an insufficient treatment.